Fan unit and air treatment system including the same

ABSTRACT

A problem to be solved by the present disclosure is to enhance the reliability of determination of occurrence or non-occurrence of surging. Whether or not surging occurs depends on front-rear differential pressure. Therefore, by determining occurrence or non-occurrence of surging on the basis of the front-rear differential pressure, a second unit can detect and avoid surging with higher accuracy than when determining by using the pressure on an outlet side of a second fan.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of PCT International Application No. PCT/JP2021/028773, filed on Aug. 3, 2021, which claims priority under 35 U.S.C. 119(a) to Patent Application No. JP 2020-134853, filed in Japan on Aug. 7, 2020 and Patent Application No. JP 2020-161151, filed in Japan on Sep. 25, 2020, all of which are hereby expressly incorporated by reference into the present application.

TECHNICAL FIELD

The present disclosure relates to a fan unit including a fan that sends heat-exchanged air.

BACKGROUND ART

A fan unit is adjusted so as to meet a required volume of air and not to cause surging even when various ducts having different resistances are connected thereto. For example, in Patent Literature 1 (Japanese Patent Unexamined publication No. 2016-166698 A), pressure on an outlet side of a fan is detected for a predetermined time, and if the fluctuation amount of the pressure is greater than or equal to a predetermined amount, it is determined that the fan is in a surging region.

SUMMARY

A fan unit according to a first aspect is a fan unit connected to a predetermined unit through a duct, and includes a fan with a variable rotation speed, a casing, a first acquisition unit, a second acquisition unit, and a control unit. The casing has an intake port and a blow-out port, and houses the fan. The first acquisition unit acquires front-rear differential pressure that is a difference in air pressure between the intake port and the blow-out port of the casing. The second acquisition unit acquires a volume of air or a wind speed of the fan. The control unit determines whether or not surging by the fan occurs on the basis of the volume of air or the wind speed and the front-rear differential pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram illustrating the configuration of an air treatment system equipped with fan units according to an embodiment of the present disclosure.

FIG. 2 is a block diagram for describing the configuration of a controller.

FIG. 3 is a graph indicating a relation between a volume of air and duct resistance using duct length as a parameter.

FIG. 4 is a graph indicating results of measuring an air volume change amount when a rotation speed of a fan motor is changed by 1 (r/m) while changing front-rear differential pressure of a second unit.

FIG. 5 is a graph indicating a relation between the volume of air and the rotation speed of the fan motor using the front-rear differential pressure as a parameter.

FIG. 6 is a graph indicating a relation between the volume of air and the rotation speed of the fan motor using the front-rear differential pressure as a parameter.

FIG. 7 is a graph indicating a relation between a wind speed and the rotation speed of the fan motor using the front-rear differential pressure as a parameter.

FIG. 8 is a graph indicating a relation between the front-rear differential pressure and a coefficient and a constant term derived from FIG. 7 .

FIG. 9 is a graph indicating a relation between the volume of air and the rotation speed of the fan motor using the front-rear differential pressure as a parameter.

FIG. 10 is a graph indicating a relation between the wind speed and the rotation speed of the fan motor.

FIG. 11 is a flowchart of air volume control.

FIG. 12 is a graph showing a relation between the volume of air and the front-rear differential pressure using the rotation speed of the fan motor of a second fan as a parameter.

FIG. 13 is a graph illustrating a curve passing through extreme value points of the respective rotation speeds illustrated in FIG. 12 .

FIG. 14 is a flowchart of surging determination control in which a second controller determines occurrence of surging and eliminates the surging.

FIG. 15 is a flowchart of surging determination control according to a modification.

FIG. 16 is a configuration diagram of an air treatment system equipped with fan units according to another embodiment.

FIG. 17 is a configuration diagram of an air treatment system equipped with fan units according to still another embodiment.

DESCRIPTION OF EMBODIMENTS (1) Overall Configuration

FIG. 1 is a configuration diagram of an air treatment system 10 equipped with fan units according to an embodiment of the present disclosure. The air treatment system 10 in FIG. 1 includes a first unit 20, a plurality of second units 30, a duct 40, and a controller 50. In the present application, for convenience of description, the fan units are referred to as the second units.

The first unit 20 includes a first fan 21. Each second unit 30 includes a second fan 31. Each second fan 31 supplies air from the second unit 30 to a target space 100.

The target space 100 is, for example, a room in a building. The room is a space where the movement of air is restricted by a floor, a ceiling, and walls, for example. The plurality of second units 30 are installed with respect to one or a plurality of target spaces 100.

In FIG. 1 , the air treatment system 10 including two second units 30 installed with respect to one target space 100 is illustrated as a typical example of the air treatment system 10 including a plurality of second units 30.

The number of second units 30 may also be three or more, and is set appropriately. The number of target spaces 100 in which the second units 30 are installed may be two or more.

The duct 40 distributes first air SA delivered from the first unit 20 by the first fan 21 to the plurality of second units 30. The duct 40 includes a main pipe 41 and branch pipes 42 branched off the main pipe 41.

FIG. 1 illustrates a case where the main pipe 41 is disposed outside the first unit 20, but the main pipe 41 may also be disposed inside the first unit 20, and may also be disposed to extend from the inside of the first unit 20 to the outside of the first unit 20.

The case where the main pipe 41 is disposed inside the first unit 20 also includes a case where a portion of a casing 26 of the first unit 20 functions as the main pipe 41. FIG. 1 illustrates an example in which the main pipe 41 has an inlet 41 a connected to the first unit 20.

The first fan 21 is disposed inside the first unit 20. Here, it is configured that all of the air blown out from the first fan 21 flows into the duct 40.

The main pipe 41 of the duct 40 also has an outlet 41 b connected to inlets 42 a of the branch pipes 42. The configuration for branching the main pipe 41 into the branch pipes 42 may be a configuration using a branch chamber.

Each second unit 30 includes a casing 33 having an intake port 33 a and a blow-out port 33 b. The branch pipes 42 have a plurality of outlets 42 b connected to intake ports 33 a of the plurality of second units 30.

Each second unit 30 is connected to the target space 100 through a ventilation path 81. The ventilation path 81 has an inlet 81 a connected to the blow-out port 33 b of the second unit 30. Each second fan 31 produces an air flow from the outlet 42 b of the duct 40 toward the inlet 81 a of the ventilation path 81, inside the second unit 30. Therefore, each second fan 31 is suctioning the first air SA from the outlet 42 b of the branch pipe 42.

Each second fan 31 can change front-rear differential pressure that is a difference in air pressure between the intake port 33 a and the blow-out port 33 b of the corresponding second unit 30 by changing a rotation speed of a motor. Assuming that the static pressure in the duct 40 is constant, each second fan 31 can increase the front-rear differential pressure in the corresponding second unit 30 by increasing the rotation speed.

If the front-rear differential pressure in the second unit 30 increases, the volume of the first air SA flowing through the ventilation path 81 increases. This change in volume of flowing air changes the supplied air volume that is blown out from an outlet 81 b of each ventilation path 81 into the target space 100.

The controller 50 includes a first controller 51 and a plurality of second controllers 52. The first controller 51 and the plurality of second controllers 52 are connected to each other.

The first controller 51 controls the rotation speed of a fan motor 21 b of the first fan 21. If the rotation speed of the first fan 21 increases, a volume of air sent by the first fan 21 increases.

One second controller 52 is provided with respect to each second unit 30. Each second controller 52 controls a volume of air of the corresponding second fan 31. Each second controller 52 stores an air volume target value received from the first controller 51.

If the supplied air volume is insufficient with respect to the air volume target value, each second controller 52 increases the rotation speed of the second fan 31. Conversely, if the supplied air volume is excessive with respect to the air volume target value, the second controller 52 reduces the rotation speed of the second fan 31.

The controller 50 obtains information about the volume of air supplied to the target space 100 by a plurality of the second fans 31. The information about the volume of air includes, for example, a necessary volume of air to be supplied into the target space 100 per second or per minute.

Each second controller 52 outputs the information about the volume of air to the first controller 51. The first controller 51 determines the output required from the first fan 21 on the basis of the obtained information about the volume of air.

(2) Detailed Configuration

(2-1) First Unit 20

The first unit 20 includes the first fan 21, a heat exchanger 22, a first air volume detector 23, a temperature sensor 24, and a water volume adjustment valve 25.

(2-1-1) Heat Exchanger 22

The heat exchanger 22 is supplied with, for example, cold water or hot water as a heat medium from a heat source unit 60. For example, the heat medium supplied to the heat exchanger 22 may be something other than cold water or hot water, such as brine.

(2-1-2) First Air Volume Detector 23

Examples of the first air volume detector 23 include an air volume sensor, a wind speed sensor, or a differential pressure sensor. In the embodiment, the first air volume detector 23 detects a volume of air sent by the first fan 21.

The first air volume detector 23 is connected to the first controller 51. The first air volume detector 23 transmits the value of the volume of air detected by the first air volume detector 23 to the first controller 51.

The volume of air detected by the first air volume detector 23 is the volume of air flowing through the main pipe 41 of the duct 40, and is also a total volume of air supplied from the plurality of second units 30 to the target space 100.

(2-1-3) Temperature Sensor 24

The temperature sensor 24 detects the temperature of the first air SA sent from the first fan 21 to the duct 40. The temperature sensor 24 is connected to the first controller 51. The temperature sensor 24 inputs the detected value to the first controller 51.

(2-1-4) Water Volume Adjustment Valve 25

The first unit 20 is connected to the target space 100 through a ventilation path 82. Second air RA passing through the ventilation path 82 and returning from the target space 100 is sent out by the first fan 21 to the duct 40 through the heat exchanger 22.

The second air RA returning from the target space 100 is the air that existed inside the target space 100. When passing through the heat exchanger 22, the returning second air RA exchanges heat with the cold water or the hot water flowing through the heat exchanger 22 to become conditioned air.

The water volume adjustment valve 25 adjusts the amount of heat imparted to the first air SA that exchanges heat in the heat exchanger 22 and is sent out to the duct 40. An opening degree of the water volume adjustment valve 25 is controlled by the first controller 51. If the opening degree of the water volume adjustment valve 25 is increased, the volume of water flowing through the heat exchanger 22 increases, so that the amount of heat to be exchanged between the heat exchanger 22 and the first air SA per unit time increases. Conversely, if the opening degree of the water volume adjustment valve 25 is decreased, the volume of water flowing through the heat exchanger 22 decreases, so that the amount of heat to be exchanged between the heat exchanger 22 and the first air SA per unit time decreases.

(2-2) Second Unit 30

The second unit 30 includes the second fan 31, a fan motor 31 b that rotates the second fan 31, and a second air volume detector 32.

Each fan motor 31 b is connected to a corresponding one of the second controllers 52, and sends the rotation speed to the second controller 52. Each second air volume detector 32 is connected to a corresponding one of the second controllers 52.

Examples of the second air volume detector 32 include an air volume sensor, a wind speed sensor, or a differential pressure sensor. In the embodiment, the second air volume detector 32 detects a volume of air sent by the second fan 31.

The second air volume detector 32 inputs the detected value of the volume of air to the second controller 52. The volume of air detected by the second air volume detector 32 is the volume of air flowing through the ventilation path 81, and is also the volume of air supplied from each second unit 30 to the target space 100.

(2-3) Remote Sensor 70

A plurality of remote sensors 70 function as temperature sensors. Each remote sensor 70 is configured to transmit data indicating the temperature of the second air RA in the target space 100 to a corresponding second controller 52.

(2-4) Controller 50

FIG. 2 is a block diagram for describing the configuration of the controller 50. The controller 50 in FIG. 2 includes the first controller 51 and the plurality of second controllers 52. The first controller 51 and the plurality of second controllers 52 are connected to each other.

(2-4-1) First Controller 51

The first controller 51 includes a processor 51 a and a memory 51 b. The processor 51 a reads an air volume control program for the first fan 21 stored in the memory 51 b, and outputs necessary commands to the first fan 21 and each second controller 52.

The memory 51 b stores detected values of the first air volume detector 23 and the temperature sensor 24 as needed in addition to the air volume control program for the first fan 21.

The processor 51 a reads the detected values of the first air volume detector 23 and the temperature sensor 24 stored in the memory 51 b, and calculates an air volume target value for the first fan 21 (a total of target air volume to be supplied to the target space 100).

The above description is an example and the present disclosure is not limited to the above content of description.

(2-4-2) Second Controller 52

Each second controller 52 includes a processor 52 a and a memory 52 b. The processor 52 a reads an air volume control program for the second fan 31 stored in the memory 52 b, and outputs necessary commands to the second fan 31.

The memory 52 b stores the air volume target value output from the first controller 51 and a detected value of the second air volume detector 32 as needed in addition to the air volume control program for the second fan 31.

The processor 52 a reads the air volume target value and the detected value of the second air volume detector 32 stored in the memory 52 b, and calculates a rotation speed target value of the second fan 31.

The above description is an example and the present invention is not limited to the above content of description.

(3) Outline of Operation of Air Treatment System 10

Each second controller 52 receives a temperature measurement value of the target space 100 from a corresponding one of the remote sensors 70 connected thereto. Each second controller 52 holds data indicating a set temperature as a temperature set value.

Each second controller 52 transmits the temperature set value and the temperature measurement value to the first controller 51. The first controller 51 determines an air volume target value for each second unit 30 on the basis of the temperature set value and the temperature measurement value. The first controller 51 transmits the value of the air volume target value to each second controller 52.

The first controller 51 determines the air volume target value for each second fan 31 according to the total of the target air volume to be supplied to the target space 100, and transmits the air volume target value to each second controller 52. Each second controller 52 adjusts the rotation speed of the second fan 31 in the corresponding second unit 30. The rotation speeds of the plurality of second fans 31 are adjusted independently from each other.

Each second controller 52 controls the rotation speed of the corresponding second fan 31 so that the supplied air volume matches the air volume target value. The plurality of second controllers 52 control the rotation speeds of the plurality of second fans 31 independently from each other. If the volume of air detected by the second air volume detector 32 is small compared to the air volume target value, each second controller 52 increases the rotation speed of the corresponding second fan 31. If the volume of air detected by the second air volume detector 32 is large compared to the air volume target value, each second controller 52 reduces the rotation speed of the corresponding second fan 31.

Specific air volume control will be described in the section of “(5) Air volume control”.

(4) In Duct Resistance

(4-1) Characteristics of Duct Resistance

The length of the duct 40 connecting the first unit 20 and the second units 30 varies depending on the positions of the intake ports of the second units 30, and also varies depending on a property in which the first unit 20 and the second units 30 are installed.

There is resistance (hereinafter, referred to as duct resistance) between the air flowing through the duct 40 and the inner surface of the duct 40, and the static pressure of the air flowing through the duct 40 is reduced by friction. The longer the duct 40, the larger the duct resistance.

FIG. 3 is a graph indicating a relation between a volume of air and the duct resistance using the duct length as a parameter. In FIG. 3 , the duct resistance changes nonlinearly with respect to the volume of air flowing through the duct 40. Accordingly, the volume of air is not proportional to the rotation speed of the fan. Therefore, the rotation speed for achieving the value of the target air volume cannot be calculated proportionally.

(4-2) Air Sending Characteristics of Second Unit 30

The difference between the static pressure at the blow-out port and the static pressure at the intake port of the second unit 30 is referred to as front-rear differential pressure of the second unit 30.

FIG. 4 is a graph indicating results of measuring an air volume change amount when the rotation speed of the fan motor 31 b is changed by 1 (r/m) while changing the front-rear differential pressure of the second unit 30. The rotation speed of the fan motor 31 b before the change is 100 (r/m).

In FIGS. 3 and 4 , when the volume of air is changed to adjust the temperature, the duct resistance fluctuates, so that the front-rear differential pressure of the second unit 30 changes. Since the volume of air that changes when the rotation speed of the fan is changed by 1 (r/m) varies depending on the situation (front-rear differential pressure) at that time, adjustment is difficult. Therefore, the target air volume may not be reached unless the rotation speed of the fan is adjusted in consideration of the change in duct resistance.

For example, as illustrated in FIG. 5 , even when the volume of air is changed from 10 (m³/min) to 15 (m³/min), the required rotation speed change amount of the fan motor 31 b varies even with the same air volume change amount as long as the duct resistance is different. This is because the duct resistance also changes depending on the change in volume of air. Therefore, an air volume adjustment function considering a change in duct resistance is required.

Furthermore, in the case where the branch pipes 42 branched off the main pipe 41 are connected to the respective second units 30 as illustrated in FIG. 1 , the front-rear differential pressure of one second unit 30 is affected by a change in volume of air of the other second unit 30 and air discharge pressure of the first unit 20.

Furthermore, as illustrated in FIG. 6 , when the volume of air of the other second unit 30 or the air discharge pressure from the first unit 20 is changed and the front-rear differential pressure is increased to the dotted line in FIG. 6 , simply maintaining the rotation speed of the fan motor 31 b leads to a decrease in the volume of air from 10 (m³/min) to 5 (m³/min). Therefore, the rotation speed of the fan motor 31 b needs to be increased in order to maintain the initial volume of air 10 (m³/min).

On the other hand, when the front-rear differential pressure is decreased to a two-dot chain line in FIG. 6 , maintaining the rotation speed of the fan motor 31 b leads to an increase in the volume of air from 10 (m³/min) to 15 (m³/min). Accordingly, the rotation speed of the fan motor 31 b needs to be reduced in order to maintain the initial volume of air 10 (m³/min).

Therefore, the second unit 30 requires also an air volume maintaining function considering a change in front-rear differential pressure.

(5) Air Volume Control

As described above, it has been found that the air volume control for one second unit 30 requires the air volume maintaining function considering the duct resistance, the volume of air of the other second unit 30, and the air discharge pressure of the first unit 20. However, the duct length varies depending on the property in which the first unit 20 and the second units 30 are installed or the installation position of the second units 30, and the duct resistance also fluctuates depending on the duct length and the volume of air flowing through the duct. Therefore, it is difficult to convert the relation between the rotation speed and the volume of air of the fan motor 31 b into data by conventional trial run adjustment.

In view of the above, the applicant focuses attention on the fact that the change in duct resistance appears as front-rear differential pressure, and has found that the rotation speed target value for the fan motor 31 b or the rotation speed change amount of the fan motor 31 b is calculated by a function using a variable obtained by acquiring information about the volume of air, a wind speed, or the front-rear differential pressure of the second unit 30, in addition to the rotation speed and the value of the target air volume of the fan motor 31 b.

This reduces the number of man-hours for a preliminary test, and eliminates the need for a trial run at the time of duct connection. An air volume control logic will be described below.

(5-1) Derivation of Front-Rear Differential Pressure ΔP

FIG. 7 is a graph indicating a relation between a wind speed V and a rotation speed N of the fan motor 31 b using front-rear differential pressure ΔP as a parameter. In FIG. 7 , when the front-rear differential pressure ΔP is the same, the rotation speed N of the fan motor 31 b can be expressed by a linear expression of the wind speed V by using a coefficient a and a constant term b.

N=a×V+b  (1)

As illustrated in FIG. 7 , when the front-rear differential pressure is constant, the equation (1) can be derived by performing a test for obtaining values of at least three points.

Furthermore, FIG. 8 is a graph indicating a relation between the front-rear differential pressure ΔP and the coefficient a and the constant term b derived from FIG. 7 . In FIG. 8 , the relation between the front-rear differential pressure ΔP and the coefficient a and the constant term b can be expressed by the following equations.

a=m×ΔP+n  (2)

b=p×ΔP+q  (3)

From the above equations (1), (2), and (3), the relation among the rotation speed N, the wind speed V, and the front-rear differential pressure ΔP is expressed by the following equation.

N=(m×ΔP+n)×V+(p×ΔP+q)  (4)

From the equation (4), the following equation is further derived.

ΔP=(N−n×V−q)/(m×V+p)  (5)

The equation (5) means that the front-rear differential pressure ΔP can be calculated by measuring the wind speed V when the fan motor 31 b of the second fan 31 operates at the rotation speed N.

Therefore, the rotation speed N of the fan motor 31 b, the wind speed V or volume of air Q of the second fan 31, and the front-rear differential pressure ΔP are parameters having a relation in which, from the two values of them, the remaining one value is derived.

(5-2) Air Volume Adjustment Function Considering Change in Duct Resistance

A calculus equation for calculating a rotation speed target value Ny can be derived from the above equation (5) and a theoretical formula of the fan. The relation among current front-rear differential pressure ΔPx, a current volume of air Qx, a front-rear differential pressure target value ΔPy, and an air volume target value Qy is expressed by an equation below from the theoretical formula of the fan.

ΔPy/ΔPx=(Qy/Qx)²  (6)

From the above equations (5) and (6), the following equation holds.

(Ny−n×Vy−q)/(m×Vy+p)=(Qy/Qx)² ×ΔPx  (7)

Furthermore, since Vy=(Qy/Qx)×Vx, the following equation holds.

Ny=(Qy/Qx)² ×ΔPx×{m×(Qy/Qx)×Vx+p}+n×(Qy/Qx)×Vx+q  (8)

Hereinafter, the equation (8) is referred to as a first function.

Technical significance of the first function will be described with reference to FIG. 9 . FIG. 9 is a graph indicating a relation between the volume of air and the rotation speed of the fan motor 31 b using the front-rear differential pressure ΔP as a parameter. In FIG. 9 , the change in duct resistance appears as a change in front-rear differential pressure ΔP.

For example, the rotation speed of the fan motor 31 b for maintaining the volume of air 10 (m³/min) at the front-rear differential pressure 50 (Pa) is 920 (r/m). If the duct resistance is constant irrespective of the volume of air, when the volume of air is changed to 15 (m³/min), the rotation speed may be simply set to 1100 (r/m).

However, the duct resistance changes by changing the volume of air. According to FIG. 9 , by changing the volume of air to 15 (m³/min), the front-rear differential pressure increases to 109.9 (Pa) due to the change in duct resistance. In order to maintain the volume of air 15 (m³/min) when the front-rear differential pressure is 109.9 (Pa), it is necessary to maintain the rotation speed of the fan motor 31 b at 1348 (r/m).

Therefore, the air volume adjustment function considering the change in duct resistance is required, and the rotation speed Ny in the first function (the above equation (8)) is the rotation speed considering the change in duct resistance.

When the air volume target value Qy, which is an instruction value of the volume of air from the first controller 51, is changed, the second controller 52 calculates the rotation speed target value for the fan motor 31 b of the second fan 31 by using the first function.

(5-3) Air Volume Adjustment Function Considering Change in Front-Rear Differential Pressure

If the front-rear differential pressure ΔP does not fluctuate even after the rotation speed of the fan motor 31 b reaches the rotation speed target value, the rotation speed is maintained. However, when the volume of air of the other second unit 30 or the air discharge pressure of the first unit 20 is changed, the front-rear differential pressure ΔP fluctuates.

FIG. 10 is a graph indicating a relation between the wind speed and the rotation speed of the fan motor 31 b. In FIG. 10 , for example, the rotation speed of the fan motor 31 b necessary to maintain the wind speed target value Vy at the front-rear differential pressure 50 (Pa) is 980 (r/m).

Here, when the front-rear differential pressure ΔP is increased to the dotted line in FIG. 10 , simply maintaining the rotation speed of the fan motor 31 b at 980 (r/m) leads to a decrease in the wind speed to Vx, so that the volume of air becomes insufficient.

In order to maintain the air volume target value, it is necessary to return the wind speed from Vx to Vy, and it is necessary to increase the rotation speed of the fan motor 31 b by 200 r/m to 1180 (r/m).

The rotation speed change amount ΔN of the fan motor 31 b is expressed by the following equation from the equations (2) and (4).

ΔN=a×(Vy−Vx)  (9)

Hereinafter, the equation (9) is referred to as a second function.

The second function is used when calculating the rotation speed change amount when the air volume target value Qy is not changed but the rotation speed of the fan motor 31 b needs to be changed due to the fluctuation of the front-rear differential pressure ΔP.

FIG. 11 is a flowchart of air volume control. The air volume control will be described below with reference to FIG. 11 .

(Step S1)

First, in step S1, the second controller 52 determines whether or not the air volume target value Qy is received from the first controller 51. When the second controller 52 receives the air volume target value Qy, the process proceeds to step S2. When the second controller 52 does not receive the air volume target value Qy, the process proceeds to step S6.

(Step S2)

Next, in step S2, the second controller 52 calculates the wind speed target value Vy for achieving the air volume target value Qy.

(Step S3)

Next, in step S3, the second controller 52 updates the wind speed target value Vy to the value calculated in step S2.

(Step S4)

Next, in step S4, the second controller 52 calculates the rotation speed target value Ny for the fan motor 31 b for achieving the wind speed target value Vy updated in step S3 using the first function.

(Step S5)

Next, in step S5, the second controller 52 updates the rotation speed target value for the fan motor 31 b to the value Ny calculated in step S4. After updating the rotation speed target value to Ny, the second controller 52 controls the rotation speed of the fan motor 31 b to reach the target value.

(Step S6)

Next, in step S6, the second controller 52 acquires a detected value of the second air volume detector 32 as a current wind speed Vx.

(Step S7)

Next, in step S7, the second controller 52 calculates the difference between the wind speed target value Vy and the current wind speed Vx.

(Step S8)

Next, in step S8, the second controller 52 calculates the front-rear differential pressure ΔP.

(Step S9)

Next, in step S9, the second controller 52 calculates a coefficient a as a control parameter.

(Step S10)

Next, in step S10, the second controller 52 calculates the rotation speed change amount ΔN by applying the difference between the wind speed target value Vy and the current wind speed Vx calculated in step S7 and the coefficient a calculated in step S9 to the second function.

(Step S11)

Next, in step S11, the second controller 52 calculates the rotation speed target value Ny on the basis of the rotation speed change amount ΔN calculated in step S10.

(Step S12)

Next, in step S12, the second controller 52 updates the rotation speed to the rotation speed target value Ny calculated in step S11. Then, the process by the second controller 52 returns to step S1.

As described above, when there is an instruction of the air volume target value from the first controller 51, a first program from step S1 to step S5 is executed, but when there is no instruction of the air volume target value from the first controller 51, a second program from step S6 to step S12 is executed.

The first program is for calculating the rotation speed target value by using the first function, and the second program is for calculating the rotation speed change amount by using the second function.

Furthermore, the rotation speed target value Ny can also be calculated by using the second function, and the second controller 52 can switch between the first program and the second program. Therefore, even when the second unit 30 acquires a new air volume target value Qy or a new wind speed target value Vy, the second unit 30 can control the rotation speed while calculating the rotation speed change amount ΔN by using the second function without using the first function.

(5-4) Surging Detection Function

(5-4-1) Occurrence Factor of Surging

FIG. 12 is a graph showing a relation between the volume of air Q and the front-rear differential pressure ΔP using the rotation speed N of the fan motor 31 b of the second fan 31 as a parameter. In FIG. 12 , the horizontal axis represents the volume of air Q, and the vertical axis represents the front-rear differential pressure ΔP.

As understood from FIG. 12 , in the second unit 30, when the volume of air Q changes in a state where the rotation speed N of the fan motor 31 b of the second fan 31 is maintained constant, the front-rear differential pressure ΔP has one extreme value at which the front-rear differential pressure ΔP changes from rising to falling. Hereinafter, a point indicating the extreme value is referred to as an extreme value point.

The volume of air at the extreme value point countervails the resistance of the duct 40 connected to the second unit 30. Accordingly, the resistance of the duct 40 decreases when the volume of air decreases from the extreme value point. Therefore, this time, the volume of air is increased and takes a value on the right side of the extreme value point. As a result, the resistance of the duct 40 increases and pushes the air back. A state where the behavior of the air is repeated in such a manner is referred to as surging.

The surging causes a periodic pressure fluctuation, which causes sound and vibration that adversely affect the equipment. Usually, the fan is used while avoiding such a volume of air and the vicinity of the volume of air. However, in the air treatment system 10 according to the embodiment, the front-rear differential pressure of one second unit 30 fluctuates due to an increase or decrease in discharge pressure of the first unit 20 and volume of air of the other second unit 30. Accordingly, the front-rear differential pressure may unintentionally reach the extreme value illustrated in FIG. 12 .

(5-4-2) Method for Determining Surging

FIG. 13 is a graph illustrating a curve passing through extreme value points of the respective rotation speeds illustrated in FIG. 12 . In FIG. 12 , surging occurs when the volume of air takes a value on the left side of the extreme value points. Therefore, surging does not occur when the combination of the volume of air and the front-rear differential pressure falls outside the region (hereinafter, referred to as surging occurrence region) surrounded by the vertical axis and the curve in FIG. 13 . The curve in FIG. 13 is expressed by the following equation.

f(Q)=r×Q ² +s×Q  (10)

“r” and “s” can be determined by experimental data.

(5-4-2-1) Determination of Surging Based on Current Volume of Air Qx

Therefore, f(Qx) calculated by substituting the current volume of air Qx into the above equation (10) corresponds to the front-rear differential pressure that can cause surging when the volume of air is Qx.

If the current front-rear differential pressure ΔPx is within a surging occurrence region, ΔPx−f(Qx)≥0. On the other hand, if the current front-rear differential pressure ΔPx is outside the surging occurrence region, ΔPx−f(Qx)<0.

(5-4-2-2) Prediction of Surging Based on Air Volume Target Value Qy

For example, when receiving an instruction signal of the air volume target value Qy from the first controller 51, the second controller 52 calculates a front-rear differential pressure target value ΔPy by substituting the air volume target value Qy and the current front-rear differential pressure ΔPx and volume of air Qx into the equation (6): ΔPy/ΔPx=(Qy/Qx)². Furthermore, the second controller 52 calculates f(Qy) by substituting the air volume target value Qy into the above equation (10).

If the front-rear differential pressure target value ΔPy is within the surging occurrence region, ΔPy−f(Qy)≥0. On the other hand, if the front-rear differential pressure target value ΔPy is outside the surging occurrence region, ΔPy−f(Qy)<0.

Therefore, whether or not the air volume target value Qy causes surging can be determined by whether or not ΔPy−f(Qy)>0.

(5-4-3) Surging Determination Control

FIG. 14 is a flowchart of surging determination control in which the second controller 52 determines occurrence of surging and eliminates the surging. In FIG. 14 , the second controller 52 performs control processing from step S21 to step S28 in parallel with control processing from step S1 to step S12 in FIG. 11 .

(Step S21)

In step S21, the second controller 52 acquires the current rotation speed Nx of the fan motor 31 b.

(Step S22)

Next, in step S22, the second controller 52 acquires a detected value of the second air volume detector 32 as the current wind speed Vx.

(Step S23)

Next, in step S23, the second controller 52 calculates the current volume of air Qx. The volume of air Qx can be calculated from the wind speed Vx.

(Step S24)

Next, in step S24, the second controller 52 calculates the current front-rear differential pressure ΔPx. The front-rear differential pressure ΔPx can be calculated by substituting the current rotation speed Nx and wind speed Vx into the equation (5).

(Step S25)

Next, in step S25, the second controller 52 calculates f(Qx). “f(Qx)” can be calculated by substituting the volume of air Qx into the equation (10).

(Step S26)

Next, in step S26, the second controller 52 determines whether or not ΔPx−f(Qx)≥0. When the second controller 52 determines that ΔPx−f(Qx)≥0, the process proceeds to step S27.

Here, the determination that “ΔPx−f(Qx)≥0” is the same as the confirmation of occurrence of surging.

On the other hand, when the second controller 52 determines that ΔPx−f(Qx)<0, the process returns to step S21 to continue the determination of the presence or absence of the occurrence of surging.

(Step S27)

Next, in step S27, the second controller 52 increases the rotation speed of the fan motor 31 b to C×Nx obtained by multiplying the current rotation speed Nx by a predetermined ratio C. The ratio C has an initial set value of 1.05, but the setting can be changed on the user side.

Here, since it is determined that ΔPx−f(Qx)≥0 and the occurrence of surging is confirmed in the preceding step S26, the second controller 52 gradually increases the rotation speed of the fan motor 31 b to eliminate the surging.

(Step S28)

Next, in step S28, the second controller 52 waits for a predetermined time, and the process returns to step S21. The purpose of waiting for a predetermined time is to secure a response time from when the rotation speed of the fan motor 31 b is increased to when the wind speed changes. The initial set value of the predetermined time is one second, but the setting can be changed on the user side.

As described above, the second controller 52 repeats the routine from step S21 to step S28 described in FIG. 14 while the air treatment system 10 is operating. In this manner, the second controller 52 monitors whether or not ΔPx−f(Qx)≥0, and when ΔPx−f(Qx)≥0, determines that surging occurs, and increases the rotation speed of the fan motor 31 b.

An advantage of the surging determination control is that the surging can be eliminated by the second controller 52 alone.

Furthermore, since the rotation speed of the fan motor 31 b is gradually increased, it is possible to avoid a situation in which too much margin is taken for the rotation speed just in order to eliminate the surging.

(6) Modification of Surging Determination Control

In the control described in FIG. 14 , after confirming the occurrence of surging, the second controller 52 alone eliminates the surging. However, in a following modification, the second controller 52 eliminates the surging in cooperation with the first controller 51.

FIG. 15 is a flowchart of surging determination control according to the modification. FIG. 15 differs from FIG. 14 in that steps S27 and S28 are replaced with steps S27 x to S32 x.

The second controller 52 performs control processing from step S21 to step S32 x in FIG. 15 in parallel with the control processing from step S1 to step S12 in FIG. 11 .

Since steps S21 to S26 have already been described, step S27 x and subsequent steps will be described here.

(Step S27 x)

In step S27 x, the second controller 52 notifies the first controller 51 that ΔPx−f(Qx)≥0. Specifically, the second controller 52 transmits a signal Sig1 set in advance and indicating that “ΔPx−f(Qx)≥0” to the first controller 51.

(Step S28 x)

Next, when receiving the signal from the second controller 52, the first controller 51 determines that surging occurs or there is a possibility that surging may occur, and sets a new air volume target value Qy and instructs the second controller 52 in order to eliminate the surging.

When the first controller 51 sets a new air volume target value Qy, the first controller 51 may set the air volume target value Qy in consideration of the volume of air of the other fan unit and a total volume of air required for the target space 100, which is an air treatment target.

(Step S29 x)

In step S29 x, the second controller 52 determines whether or not the air volume target value Qy is received from the first controller 51. When the second controller 52 receives the air volume target value Qy, the process proceeds to step S30 x.

(Step S30 x)

Next, in step S30 x, the second controller 52 calculates the front-rear differential pressure target value ΔPy. The front-rear differential pressure target value ΔPy can be calculated by substituting the air volume target value Qy and the current front-rear differential pressure ΔPx and volume of air Qx into the equation (6).

(Step S31 x)

Next, in step S31 x, the second controller 52 calculates f(Qy). “f(Qy)” can be calculated by substituting the air volume target value Qy into the equation (10).

(Step S32 x)

Next, in step S32 x, the second controller 52 determines whether or not ΔPy−f(Qy)≥0.

When determining that ΔPy−f(Qy)≥0, the second controller 52 determines that the surging cannot be eliminated, and the process returns to step S27 x to notify the first controller 51 that ΔPy−f(Qy)≥0.

Specifically, the second controller 52 transmits a signal Sig2 set in advance and indicating that “ΔPy−f(Qy)≥0” to the first controller 51. Here, the determination that “ΔPy−f(Qy)≥0” is the same as the possibility of occurrence of surging.

On the other hand, when the second controller 52 determines that ΔPy−f(Qy)<0, the process returns to step S21 to continue the determination of the presence or absence of the occurrence of surging.

When the air volume target value Qy is reset and transmitted to the second controller 52, control processing from step S1 to step S12 in FIG. 11 is performed.

Thereafter, the second controller 52 repeats the routine from step S21 to step S32 x described in FIG. 15 to monitor the presence or absence of the occurrence of surging.

(7) Features

(7-1)

Whether or not surging occurs depends on the front-rear differential pressure. Therefore, by determining occurrence or non-occurrence of surging on the basis of the front-rear differential pressure, the second unit 30 can detect and avoid surging with higher accuracy than when determining by using the pressure on the outlet side of the second fan 31.

(7-2)

The second controller 52 can determine occurrence or non-occurrence of surging by a simple means of comparing the current front-rear differential pressure ΔPx with an allowable upper limit value of the front-rear differential pressure at the current rotation speed Nx. Therefore, the second unit 30 does not need to be newly provided with a dedicated sensor.

(7-3)

In the second unit 30, a relational expression: f(Q)=r×Q²+s×Q can be obtained only by measuring at least three extreme values on curves expressing a relation between the volume of air of the second fan and the front-rear differential pressure that are measured for each rotation speed of the second fan 31, making it easy to adapt to each model.

(7-4)

In the second unit 30, when determining that surging by the second fan 31 occurs, the second controller 52 increases the rotation speed of the second fan 31. Since the second unit can alone increase the rotation speed, it is easy to avoid surging.

(7-5)

Even if surging is avoided by, for example, increasing the rotation speed by using one second unit 30 alone, there is a possibility that the other fan unit connected through the duct 40 causes surging due to a change in front-rear differential pressure in the other fan unit. Furthermore, the air volume target value Qy cannot be set irrespective of the total volume of air required for the target space 100, which is an air treatment target. Therefore, in the air treatment system 10, the first controller 51 determines the air volume target value Qy for the second unit 30 for avoiding surging in consideration of the total volume of air required for the target space 100, which is an air treatment target. As a result, the reliability of surging elimination is high.

(8) Other Embodiment

The first unit 20 includes the first fan 21 in the above embodiment, but the first unit 20 does not necessarily need the first fan 21. The air volume control according to the present disclosure is also applicable to a second unit connected to a first unit not including a fan through a duct.

Specific examples will be described below.

(8-1)

FIG. 16 is a configuration diagram of an air treatment system 110 equipped with fan units according to another embodiment. The air treatment system 110 in FIG. 16 is disposed behind a ceiling of a floor of a building BL, and ventilates a room. The air treatment system 110 includes a first unit 120 as an air treatment unit, second units 130 as air supply fan units, and third units 135 as air exhaust fan units.

The air treatment system 110 further includes an outdoor air duct 150, a supply air duct 160, a return air duct 170, and an exhaust air duct 180. The outdoor air duct 150, the supply air duct 160, the return air duct 170, and the exhaust air duct 180 are connected to the first unit 120.

The outdoor air duct 150 constitutes an air flow path leading from an opening 104 leading to the outside of the building BL to the first unit 120. The supply air duct 160 constitutes an air flow path leading from the first unit 120 to blow-out ports 102 provided in the room.

The return air duct 170 constitutes an air flow path leading from intake ports 103 provided in the room to the first unit 120. The exhaust air duct 180 constitutes an air flow path leading from the first unit 120 to an opening 105 leading to the outside of the building BL.

The supply air duct 160 includes a single main duct 161 and a plurality of branch ducts 162 branched off the main duct 161 via a branch chamber 191.

The return air duct 170 includes a single main duct 171 and a plurality of branch ducts 172 branched off the main duct 171 via a branch chamber 192.

The first unit 120 removes dust in air passing through the unit, changes temperature of the air, changes humidity of the air, and removes predetermined chemical composition and a predetermined pathogen in the air.

The second units 130 are connected to the supply air duct 160. The third units 135 are connected to the corresponding return air duct 170.

In the air treatment system 110, the first unit 120 does not include any fan, so that the second units 130 and the third units 135 generate a flow of air in the first unit 120.

Therefore, a change in front-rear differential pressure of one second unit 130 is mainly caused by changes in volume of air of fans of other second units 130. Furthermore, a change in front-rear differential pressure of one third unit 135 is mainly caused by a change in volume of air of a fan of the other third unit 135.

In the air treatment system 110, the “front-rear differential pressure” is introduced as a variable of the calculation formula for the rotation speed target value similarly to the above embodiment. Accordingly, it is possible to reflect the change in duct resistance that changes from moment to moment in the calculation of the air volume target value, and to shorten the response time of the output value (volume of air) to the input value (rotation speed).

Furthermore, in the air treatment system 110, whether or not surging occurs depends on the front-rear differential pressure. A second controller 152 in the second unit 130 or a third controller 153 in the third unit 135 can determine occurrence or non-occurrence of surging by a simple means of comparing the current front-rear differential pressure with the allowable upper limit value of the front-rear differential pressure at the current rotation speed. Therefore, the air treatment system 110 does not need to be newly provided with a dedicated sensor just to detect the occurrence of surging.

FIG. 17 is a configuration diagram of an air treatment system 210 equipped with fan units according to still another embodiment. The air treatment system 210 in FIG. 17 is disposed behind a ceiling of a floor of a building.

The air treatment system 210 differs from the air treatment system 10 in FIG. 1 in that the first unit does not include a first fan, and other configurations are the same as those of the air treatment system 10 in FIG. 1 . Therefore, components same as those of the air treatment system 10 in FIG. 1 will be denoted by the same reference signs and description thereof is omitted.

A utilization-side heat exchanger 22 of a first unit 220 is supplied with heat energy required for heat exchange from the heat source unit 60. The first unit 220 generates conditioned air through heat exchange in the utilization-side heat exchanger 22.

The first unit 220 is connected to the duct 40. The duct 40 includes the main pipe 41 and the branch pipes 42. The main pipe 41 has one end connected to the first unit 220. The main pipe 41 has the other end branched and connected to a plurality of branch pipes 42. Each branch pipe 42 has a terminal end connected to one second unit 30.

Each second unit 30 includes a second fan 31. The second fan 31 rotates to suck the conditioned air generated in the first unit 220 into the second unit 30 through the duct 40, and then supplies the conditioned air to the target space 100.

A fan motor 31 b of each second fan 31 is configured to change the rotation speed individually. Each fan motor 31 a changes the rotation speed individually to change the supply air volume of the corresponding second unit 30 individually.

In the air treatment system 210, the first unit 220 does not include any fan, so that the second units 30 generate a flow of air in the first unit 220.

Therefore, the change in front-rear differential pressure of one second unit 30 is mainly caused by a change in volume of air of the second fan 31 of the other second unit 30. However, since the “front-rear differential pressure” is introduced as a variable of the calculation formula for the rotation speed target value, it is possible to reflect the change in duct resistance that changes from moment to moment in the calculation of the air volume target value, and to shorten the response time of the output value (volume of air) to the input value (rotation speed).

Furthermore, in the air treatment system 210, whether or not surging occurs depends on the front-rear differential pressure. The second controller 52 in the second unit 30 can determine occurrence or non-occurrence of surging by a simple means of comparing the current front-rear differential pressure with the allowable upper limit value of the front-rear differential pressure at the current rotation speed. Therefore, the air treatment system 210 does not need to be newly provided with a dedicated sensor just to detect the occurrence of surging.

(9) Others

(9-1)

In the above embodiment and modifications, the front-rear differential pressure is calculated on the basis of the wind speed or the volume of air acquired from the second air volume detector 32. However, the front-rear differential pressure value may be calculated from sensor values of pressure sensors respectively disposed at the intake port and the blow-out port of the second unit, and the wind speed value may be obtained from the front-rear differential pressure and the rotation speed.

(9-2)

In FIG. 7 , changes in wind speed of a fan when the rotation speed of a fan motor is changed are observed at five front-rear differential pressures. This is utilized as data for deriving a relational expression of the rotation speed, the wind speed, and the front-rear differential pressure, but does not necessarily require data for five front-rear differential pressures, and the relational expression can be derived if there is data for at least three front-rear differential pressures.

The embodiment of the present disclosure has been described above. It will be understood that various changes to modes and details can be made without departing from the spirit and scope of the present disclosure recited in the claims.

EXPLANATION OF REFERENCES

-   -   10: air treatment system     -   20: first unit (air treatment unit)     -   30: second unit (fan unit)     -   31: second fan (fan)     -   31 b: fan motor     -   32: second air volume detector (second acquisition unit)     -   33: casing     -   33 a: intake port     -   33 b: blow-out port     -   40: duct     -   50: controller (control unit)     -   51: first controller (first control unit, third acquisition         unit)     -   52: second controller (second control unit, first acquisition         unit)     -   110: air treatment system     -   120: first unit     -   130: second unit (fan unit)     -   135: third unit (fan unit)     -   160: supply air duct (duct)     -   170: return air duct (duct)     -   210: air treatment system

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent Unexamined publication No.     2016-166698 A 

1. A fan unit connected to a predetermined unit through a duct, the fan unit comprising: a fan with a variable rotation speed; a casing that has an intake port and a blow-out port and houses the fan; a first acquisition unit that acquires front-rear differential pressure that is a difference in air pressure between the intake port and the blow-out port of the casing; a second acquisition unit that acquires a volume of air or a wind speed of the fan; and a controller that determines whether or not surging by the fan occurs on a basis of the volume of air or the wind speed and the front-rear differential pressure.
 2. The fan unit according to claim 1, wherein the controller stores in advance a first relational expression that derives an allowable upper limit value of the front-rear differential pressure with respect to the volume of air of the fan, and the controller further determines whether or not surging by the fan occurs by comparing the allowable upper limit value of the front-rear differential pressure calculated on the basis of the volume of air acquired by the second acquisition unit and the first relational expression with the front-rear differential pressure acquired by the first acquisition unit.
 3. The fan unit according to claim 2, wherein the first relational expression is expressed by a curve passing through extreme values on curves expressing a relation between the volume of air of the fan and the front-rear differential pressure that are measured for each rotation speed of a fan motor of the fan.
 4. The fan unit according to claim 1, wherein when determining that surging by the fan occurs, the controller increases the rotation speed of the fan motor of the fan.
 5. An air treatment system comprising: an air treatment unit that performs a predetermined treatment to air; and the fan unit according to claim 1, the fan unit being connected to the air treatment unit through the duct, wherein the controller includes a first controller provided in the air treatment unit, and a second controller provided in the fan unit, when determining that surging occurs, the second controller transmits a first signal to the first controller, when receiving the first signal, the first controller determines a volume of air of the fan unit that eliminates the surging and transmits the volume of air to the second controller as an air volume target value, and the second controller controls a rotation speed of the fan motor of the fan unit on a basis of the air volume target value.
 6. The fan unit according to claim 2, wherein when determining that surging by the fan occurs, the controller increases the rotation speed of the fan motor of the fan.
 7. The fan unit according to claim 3, wherein when determining that surging by the fan occurs, the controller increases the rotation speed of the fan motor of the fan.
 8. An air treatment system comprising: an air treatment unit that performs a predetermined treatment to air; and the fan unit according to claim 2, the fan unit being connected to the air treatment unit through the duct, wherein the controller includes a first controller provided in the air treatment unit, and a second controller provided in the fan unit, when determining that surging occurs, the second controller transmits a first signal to the first controller, when receiving the first signal, the first controller determines a volume of air of the fan unit that eliminates the surging and transmits the volume of air to the second controller as an air volume target value, and the second controller controls a rotation speed of the fan motor of the fan unit on a basis of the air volume target value.
 9. An air treatment system comprising: an air treatment unit that performs a predetermined treatment to air; and the fan unit according to claim 3, the fan unit being connected to the air treatment unit through the duct, wherein the controller includes a first controller provided in the air treatment unit, and a second controller provided in the fan unit, when determining that surging occurs, the second controller transmits a first signal to the first controller, when receiving the first signal, the first controller determines a volume of air of the fan unit that eliminates the surging and transmits the volume of air to the second controller as an air volume target value, and the second controller controls a rotation speed of the fan motor of the fan unit on a basis of the air volume target value.
 10. An air treatment system comprising: an air treatment unit that performs a predetermined treatment to air; and the fan unit according to claim 4, the fan unit being connected to the air treatment unit through the duct, wherein the controller includes a first controller provided in the air treatment unit, and a second controller provided in the fan unit, when determining that surging occurs, the second controller transmits a first signal to the first controller, when receiving the first signal, the first controller determines a volume of air of the fan unit that eliminates the surging and transmits the volume of air to the second controller unit as an air volume target value, and the second controller controls a rotation speed of the fan motor of the fan unit on a basis of the air volume target value. 